A process of forming a master for optical disks, generally referred to as xe2x80x9cmasteringxe2x80x9d, is where a nickel or the like metallic master, i.e., xe2x80x9cstamperxe2x80x9d, is formed at its final step. A large number of optical disks are duplicated with use of the stamper as a mold in a succeeding molding process. Through dry etching, the present invention relates to a direct dry mastering stamper for optical disks, a method and an apparatus for direct dry mastering a stamper for optical disks whereby the stamper is manufactured in a reduced number of steps in a short time at low costs with a high yield as compared with the prior art, and an optical disk formed with use of the stamper.
A conventional mastering process will be described with reference to FIGS. 5A-5G.
In FIG. 5A, 31 is a glass substrate to which a positive type photoresist is applied thereby forming a resist layer 32. A signal-modulated laser beam 3 is converged to a size of sub microns by a recording lens 4 to expose the glass substrate as shown in FIG. 5B. A developing solution is applied from a nozzle 33 onto the glass substrate 31, whereby the exposed part is etched and removed, as shown in FIG. 5C. Fine dents 34 called xe2x80x9cpitsxe2x80x9d, namely, signal pits, are formed on the photoresist layer 32. The glass substrate 31 is then heated by baking, so that a film of the photoresist layer 32 is stabilized (FIG. 5D). A metallic conductive coat 35 is formed onto the photoresist layer 32 by sputtering or the like manner (FIG. 5E). Thereafter, with using the metallic conductive coat 35 as an electrode, nickel plating is carried out when a nickel thick film 36 of a thickness of approximately 0.3 mm is formed on the metallic conductive coat 35 (FIG. 5F). A replica of the pits on the photoresist layer is formed to the nickel thick film 36.
The nickel thick film 36 is peeled off the glass base 31 as shown in FIG. 5G. A rear face of the thick film is polished, and inner and outer diameters are punched to conform to a molding machine. An optical disk master, that is, stamper, is thus completed.
The mastering process of forming the stamper as described hereinabove includes chemical treatment steps such as development, electroforming, and the like. In general, the chemical treatment is varied in quality and worsened in yield without strict management on production environments such as chemical liquids to be used, devices to be used, temperatures, humidities, and the like. According to the inventors"" experience, further, a wet process such as the aforementioned ones cause defects on the stamper with high probability because most surface foreign particles and specks adhere or are generated when the stamper is dried from the wet state. Particularly, in accordance with a signal density increase of optical disks, the pits are required to be formed in a micro-structure of a size of sub microns, and therefore, even a minute speck or a little quantity of adhering foreign particles impairs the stamper.
Pits are formed in a chemical liquid in the conventional process. More specifically, the pits are formed to a front face of the resist layer in the developing solution and signal projections of nickel along the pits are formed in the plating solution. Under these circumstances, a degree of cleanness is hard to manage and the foreign particles or the like are prone to adhere.
Then, the pits (dents) formed to the photoresist layer on the glass base through exposure and development are transferred as projections (bumps) to a metal plate of nickel by electroforming to form the stamper. The number of steps is large and, a quality and a yield are decreased due to defects brought about in the process. Facility costs and material costs are also disadvantageously high.
The object of the present invention is, therefore, to provide a direct dry mastering stamper for optical disks, a method and an apparatus for direct dry mastering a stamper for optical disks whereby a degree of cleanness is easy to manage, adhesion of foreign particles or the like can be reduced, the number of production steps for the stamper is reduced by directly dry etching a metallic, ceramic, or the like substrate without electroforming or the like process, and a quality and a productivity can be improved and, an optical disk formed with use of the stamper.
In order to achieve the aforementioned objective, the present invention is constituted as follows.
According to a first aspect of the present invention, there is provided a method for mastering a stamper for optical disks. The method includes: irradiating laser beams signal-modulated and converged by a recording lens to a surface of a substrate while rotating the substrate having a resist layer formed of a negative type photoresist, thereby forming exposed and unexposed parts; thereafter, continuously executing heating, developing in a dry process, etching in a dry process, and removing the resist in a dry process, thereby forming signal projections to the surface of the substrate; and thereafter, machining the substrate to a stamper size conforming to a mold of an optical disk-molding machine, thereby forming an optical disk stamper.
According to a second aspect of the present invention, there is provided a method for mastering a stamper for optical disks. This method includes: irradiating laser beams signal-modulated and converged by a recording lens to a surface of a substrate while rotating the substrate having a resist layer formed of a negative type resist and machined to a stamper size conforming to a mold of an optical disk-molding machine, thereby forming exposed and unexposed parts; and thereafter, heating, and then carrying out developing in a dry process, etching in a dry process, and removing the resist in a dry process, thereby forming an optical disk stamper.
According to a third aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the heating after irradiating the laser beams is carried out in an organic Si gas ambience of hexamethyl dislazane or the like.
According to a fourth aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the developing, the etching, and the removing of the resist are carried out in the same chamber by changing reaction gases.
According to a fifth aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the stamper substrate having the negative type resist layer provided to a front face thereof is formed of a material essentially consisting of at least one of nickel, chromium, aluminum, titanium, cobalt, iron, molybdenum, tungsten, boron, copper, and tantalum.
According to a sixth aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the stamper substrate having the negative type resist layer provided to a front face thereof is formed of a silicon compound of Si, SiO2, SiC, or the like.
According to a seventh aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the stamper substrate having the negative type resist layer provided to a front face thereof is formed of glass.
According to an eighth aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the stamper substrate having the negative type resist layer provided to a front face thereof is formed of a material essentially consisting of carbon.
According to a ninth aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the dry etching layer of the stamper substrate having the negative type resist layer provided to a front face thereof is formed of titanium nitride, titanium oxide, tantalum, tungsten, chromium, molybdenum, cobalt, boron, nickel phosphor, nickel boron, or nickel cobalt.
According to a 10th aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the ninth aspect, wherein the stamper substrate is constructed in a double layer structure of a base layer and a dry etching layer which is disposed on the base layer and is to be partly removed by dry etching thereby forming the signal projections, and a thickness of the dry etching layer is equal to an etching depth at the etching.
According to an 11th aspect of the present invention, there is provided an apparatus for mastering a stamper for optical disks. The apparatus comprises: a rotating apparatus for rotating a stamper substrate having a resist layer of a negative type photoresist provided to a front face thereof; and an exposing apparatus for irradiating laser beams signal-modulated and converged by a recording lens to the front face of the rotating stamper substrate, thereby forming exposed and unexposed parts. In addition, the apparatus comprises a processing apparatus for, after the irradiation, continuously carrying out heating, developing in a dry process, etching in a dry process, and removing the resist in a dry process, thereby forming signal projections to the front face of the stamper substrate; and a machining apparatus for machining the stamper substrate to a stamper size conforming to a mold of an optical disk-molding machine, thereby forming an optical disk stamper.
According to a 12th aspect of the present invention, there is provided an apparatus for mastering a stamper for optical disks. The apparatus comprises: a rotating apparatus for rotating a stamper substrate having a resist layer of a negative type resist provided to a front face thereof and machined to a stamper size conforming to a mold of an optical disk-molding machine; an exposing apparatus for irradiating laser beams signal-modulated and converged by a recording lens to the front face of the rotating stamper substrate, thereby forming exposed and unexposed parts; and a processing apparatus for, after the irradiation, carrying out heating, developing in a dry process, etching in a dry process and removing the resist in a dry process, thereby forming an optical disk stamper.
According to a 13th aspect of the present invention, there is provided an apparatus for mastering a stamper for optical disks according to the 11th aspect, wherein the processing apparatus carries out the heating after irradiating laser beams in an organic Si gas ambience of hexamethyl disilazane or the like.
According to a 14th aspect of the present invention, there is provided an apparatus for mastering a stamper for optical disks according to the 11th aspect, wherein the processing apparatus carries out the developing, the etching, and the removing the resist in the same chamber by changing reaction gases alone.
According to a 15th aspect of the present invention, there is provided an apparatus for mastering a stamper for optical disks according to the 11th aspect, wherein the stamper substrate having the negative type resist layer provided to the front face thereof is formed of a material essentially consisting of at least one of nickel, chromium, aluminum, titanium, cobalt, iron, molybdenum, tungsten, boron, copper, and tantalum.
According to a 16th aspect of the present invention, there is provided an apparatus for mastering a stamper for optical disks according to the 11th aspect, wherein the stamper substrate having the negative type resist layer provided to the front face thereof is formed of a silicon compound of Si, SiO2, SiC, or the like.
According to a 17th aspect of the present invention, there is provided an apparatus for mastering a stamper for optical disks according to the 11th aspect, wherein the stamper substrate having the negative type resist layer provided to the front face thereof is formed of glass.
According to an 18th aspect of the present invention, there is provided an apparatus for mastering a stamper for optical disks according to the 11th aspect, wherein the stamper substrate having the negative type resist layer provided to the front face thereof is formed of a material essentially consisting of carbon.
According to a 19th aspect of the present invention, there is provided an apparatus for mastering a stamper for optical disks according to the 11th aspect, wherein the stamper substrate having the negative type resist layer provided to the front face thereof is constructed in a double layer structure of a base layer and a dry etching layer which is disposed on the base layer and is to be partly removed by dry etching thereby forming the signal projections, and the dry etching layer is formed of titanium nitride, titanium oxide, tantalum, tungsten, chromium, molybdenum, cobalt, boron, nickel phosphor, nickel boron, or nickel cobalt.
According to a 20th aspect of the present invention, there is provided an apparatus for mastering a stamper for optical disks according to the 19th aspect, wherein the stamper substrate is constructed in a double layer structure of the base layer and the dry etching layer which is disposed on the base layer and is to be partly removed by dry etching thereby forming the signal projections, and a thickness of the dry etching layer is equal to an etching depth at the etching.
According to a 21st aspect of the present invention, there is provided a mastering stamper for use in molding optical disks with using a stamper substrate itself as the stamper, which is formed by irradiating signal-modulated laser beams to a rotating stamper substrate having a resist layer provided to a front face thereof, heating the resist layer on the stamper substrate, thereafter removing exposed parts or unexposed parts of the resist layer by developing thereby forming, to the resist layer, projecting parts for forming signal projections, and forming signal projections to the stamper substrate by dry etching using the resist layer having the formed projecting parts as a signal projection form mask, the stamper substrate being constituted of a material of a (xcfx81xc3x97c) value larger than a (xcfx81xc3x97c) value of glass wherein xcfx81 is a density and c is a specific heat.
According to a 22nd aspect of the present invention, there is provided a mastering stamper for use in molding optical disks using a stamper substrate itself as the stamper, which is formed by irradiating signal-modulated laser beams to a rotating stamper substrate having a resist layer provided to a front face thereof, heating the resist layer on the stamper substrate, thereafter removing exposed parts or unexposed parts of the resist layer by developing thereby forming, to the resist layer, projecting parts for forming signal projections, and forming signal projections to the stamper substrate by dry etching using the resist layer having the formed projecting parts as a signal projection form mask, the stamper substrate being constituted of a material of a thermal diffusivity larger than a thermal diffusivity of glass.
According to a 23rd aspect of the present invention, there is provided a mastering stamper according to the 21st aspect, wherein the stamper substrate is constituted of a material with a (xcfx81xc3x97c) value not smaller than 2268 kJ/m3xc2x7deg.
According to a 24th aspect of the present invention, there is provided a mastering stamper according to the 22nd aspect, wherein the stamper substrate is constituted of a material with a thermal diffusivity larger than 0.0012 m2/h.
According to a 25th aspect of the present invention, there is provided a mastering stamper according to the 21st aspect, wherein the stamper substrate is constructed in a double layer structure of a base layer and a dry etching layer which is disposed on the base layer and is to be partly removed by dry etching thereby forming the signal projections.
According to a 26th aspect of the present invention, there is provided an optical disk manufactured with the use of the mastering stamper according to the 21st aspect.
According to a 27th aspect of the present invention, there is provided a method for mastering a stamper for optical disks for use in molding optical disks using a stamper substrate itself as the stamper. The method includes: irradiating signal-modulated laser beams with reducing thermal influences by heat of the stamper substrate stored at the irradiation of laser beams because of characteristics of a material itself of the stamper substrate while rotating the stamper substrate formed of a material with a (xcfx81xc3x97c) value larger than a (xcfx81xc3x97c) value of glass wherein xcfx81 is a density and c is a specific heat and having a resist layer provided to a front face thereof; heating the resist layer on the stamper substrate; removing exposed parts or unexposed parts of the resist layer by developing, thereby forming, to the resist layer, projecting parts for forming signal projections; and forming signal projections to the stamper substrate by dry etching with using the resist layer having the formed projecting parts as a signal projection form mask.
According to a 28th aspect of the present invention, there is provided a method for mastering a stamper for optical disks for use in molding optical disks with using a stamper substrate itself as the stamper. The method includes: irradiating signal-modulated laser beams with reducing thermal influences by heat of the stamper substrate stored at the irradiation of laser beams because of characteristics of a material itself of the stamper substrate while rotating the stamper substrate formed of a material with a thermal diffusivity larger than a thermal diffusivity of glass and having a resist layer provided to a front face thereof; heating the resist layer on the stamper substrate; removing exposed parts or unexposed parts of the resist layer by developing, thereby forming, to the resist layer, projecting parts for forming signal projections; and forming signal projections to the stamper substrate by dry etching using the resist layer having the formed projecting parts as a signal projection form mask.
According to a 29th aspect of the present invention, there is provided a direct mastering stamper according to the 25th aspect, wherein a thermal conductivity of the base layer of the stamper substrate is larger than a thermal conductivity of the etching layer.
According to a 30th aspect of the present invention, there is provided a direct mastering stamper according to the 29th aspect, wherein the base layer of the stamper substrate is formed of nickel, and the etching layer is formed of tantalum.
According to a 31st aspect of the present invention, there is provided a direct mastering stamper according to the 29th aspect, wherein the base layer of the stamper substrate is formed of aluminum or copper, and the etching layer is formed of tungsten or molybdenum.
According to a 32nd aspect of the present invention, there is provided an optical disk manufactured with the use of the direct mastering stamper according to the 29th aspect.
According to a 33rd aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein a breadth or a length of the signal projection form projecting part of the resist formed on the stamper substrate after the developing is made larger than a breadth or a length of a signal pit of the optical disk.
According to a 34th aspect of the present invention, there is provided an apparatus for mastering a stamper for optical disks according to the 11th aspect, wherein a breadth or a length of the signal projection form projecting part of the resist formed on the stamper substrate after the developing is made larger than a breadth or a length of a signal pit of the optical disk.
According to a 35th aspect of the present invention, there is provided a method for mastering a stamper for optical disks for use in molding optical disks using a stamper substrate itself as the stamper, which is formed by irradiating signal-modulated laser beams to the rotating stamper substrate having a resist layer provided to a front face thereof, heating the resist layer on the stamper substrate, thereafter removing exposed parts or unexposed parts of the resist layer by developing thereby forming, to the resist layer, projecting parts for forming signal projections, and forming signal projections to the stamper substrate by dry etching with using the resist layer having the formed projecting parts as a signal projection form mask, wherein a breadth or a length of the signal projection form projecting part of the resist formed on the stamper substrate after the developing is made larger than a breadth or a length of a signal pit of the optical disk.
According to a 36th aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the 33rd aspect, wherein a tilt angle of a side wall of the signal projection form projecting part of the resist formed on the stamper substrate after the developing is made equal to or sharper than a tilt angle of a side wall of the signal pit of the optical disk.
According to a 37th aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the 33rd aspect, wherein a breadth or a length of the signal projection form projecting part of the resist is made larger than a breadth or a length of the signal pit of the optical disk by at least a value inversely proportional to a select ratio at the time of dry etching the resist and the stamper substrate.
According to a 38th aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the 33rd aspect, wherein a tilt angle of a side wall of the signal projection form projecting part of the resist is made smaller than a tilt angle of a side wall of the signal pit of the optical disk by at least a value inversely proportional to a select ratio at the time of dry etching the resist and the stamper substrate.
According to a 39th aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the 33rd aspect, wherein the laser beams are irradiated so that a time width of a recording signal pulse of the laser beams is made longer than a time necessary for a signal pit length of the optical disk by at least a value inversely proportional to a select ratio at the time of dry etching the resist and the stamper substrate.
According to a 40th aspect of the present invention, there is provided a stamper for optical disks manufactured by the mastering method according to the 33rd aspect.
According to a 41st aspect of the present invention, there is provided a mastering stamper for optical disks to be used in molding optical disks using a stamper substrate itself as the stamper, which is formed by irradiating signal-modulated laser beams to the rotating stamper substrate having a resist layer provided to a front face thereof, heating the resist layer on the stamper substrate, thereafter removing exposed parts or unexposed parts of the resist layer by developing thereby forming, to the resist layer, projecting parts for forming signal projections, and forming signal projections to the stamper substrate by dry etching using the resist layer having the formed projecting parts as a signal projection form mask, wherein a breadth or a length of the signal projection form projecting part of the resist formed on the stamper substrate after the developing is made larger than a breadth or a length of a signal pit of the optical disk.
According to a 42nd aspect of the present invention, there is provided an optical disk manufactured with the use of the mastering stamper according to the 40th aspect.